1 <html devsite> 2 <head> 3 <title>Working with Devices</title> 4 <meta name="project_path" value="/_project.yaml" /> 5 <meta name="book_path" value="/_book.yaml" /> 6 </head> 7 <body> 8 <!-- 9 Copyright 2017 The Android Open Source Project 10 11 Licensed under the Apache License, Version 2.0 (the "License"); 12 you may not use this file except in compliance with the License. 13 You may obtain a copy of the License at 14 15 http://www.apache.org/licenses/LICENSE-2.0 16 17 Unless required by applicable law or agreed to in writing, software 18 distributed under the License is distributed on an "AS IS" BASIS, 19 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 20 See the License for the specific language governing permissions and 21 limitations under the License. 22 --> 23 24 25 26 <p>Trade Federation uses an abstraction called 27 <code><a href="/reference/com/android/tradefed/device/ITestDevice.html">ITestDevice</a></code> to 28 run tests. This abstraction objectifies the lowest-common-denominator Android device:</p> 29 <ul> 30 <li>It has a serial number</li> 31 <li>It has a state: Online, Available, Recovery, or Not Available</li> 32 <li>It has some notion of reliability. For instance, if we run a command, we can differentiate 33 between the case where the command hasn't finished yet, the case where the device doesn't support 34 running commands, and the case where the device has become unresponsive while running the 35 command.</li> 36 </ul> 37 38 <h2>Different Classes of Devices</h2> 39 <p>The three primary implementations of <code>ITestDevice</code> represent three common 40 usecases.</p> 41 42 <h3>Physical Device</h3> 43 <p>This is an actual piece of hardware, connected to the TF host machine either by USB, or by using 44 adb's TCP feature. The <a href="/reference/com/android/tradefed/device/TestDevice.html" 45 >TestDevice</a> class sits atop the ddmlib library, which is a Java interface to adb. So any 46 physical device listed in <code>adb devices</code> can be instantiated and used as a 47 <code>TestDevice</code>. 48 </p> 49 50 <h3>Emulator</h3> 51 <p>Emulators are handled specially by TF because they live in another process. To interact with an 52 Emulator, specify the <code>--emulator</code> argument for the command. See 53 <a href="/reference/com/android/tradefed/build/LocalSdkBuildProvider.html" 54 >LocalSdkBuildProvider</a> and 55 <a href="/reference/com/android/tradefed/targetprep/SdkAvdPreparer.html" 56 >SdkAvdPreparer</a> for more info.</p> 57 58 <h3>No Device</h3> 59 <p>Suppose you have a test that doesn't interact with a device at all. For instance, it might just 60 download a file from some service and verify that the file itself is valid. The 61 <a href="/reference/com/android/tradefed/device/NullDevice.html" 62 >NullDevice</a> is an <code>ITestDevice</code> that is just a stub. It has a serial number like 63 <code>null-device-N</code>, and most attempted operations either no-op silently or throw. 64 </p> 65 66 </body> 67 </html> 68
